[Chimera-users] constrain measurement of rotation to a particular axis?

Hi all, When using the “measure rotation” command, is there any way to constrain the rotation to be measured about a particular axis? I am thinking specifically of a case where I have multiple structures of a protein with different inter domain hinge angles - I can use chimera to measure the hinge angle, but for each pair of structures it chooses a slightly different rotation axis, whereas I would like to keep the same axis so I can directly compare the rotation observed between pairs of structures. Or perhaps there is there another way to do this that would make more sense? Suggestions are welcome... Best, Oliver.